The invention relates to a valve construction and mode of operation for controlling the flow of a pressure fluid from an upstream source of high pressure supply to an outlet for downstream storage or utilization at reduced pressure. The invention has illustrative application as a regulating valve, wherein the upstream supply pressure is, at least initially, in the order of 10,000 psi, and wherein a relatively small-volume tank is to be loaded with smoothly ramped increasing pressure to a set point in the order of 800 psi, the valve being automatically modulated as needed to maintain tank ullage pressure in an operating band of .+-.50 psi, during step-off demands for operating fluid from the tank.
For the indicated illustrative application of the invention, it was proposed to employ a motor-driven ball-screw system to develop requisite axial displacement for the valve member, with a lead of helical ball-screw advance in the order of 0.005 inch/revolution. But this was not possible, because the smallest ball screw available to carry the involved 10,000 psi unbalanced load has a lead of 1-mm/rev. (0.0394 inch/rev.). Thus, a single ball-screw design would place excessive torque and mass requirements on the motor, totally inconsistent with a design objective of minimizing bulk of the valve system.
In the present description, for convenience of reference, the central axis of the valve system will be sometimes referred to as "vertical", thus justifying use of the words "upper" and "lower" in connection with various component parts. But it will be understood that a "vertical" orientation is not necessary for operation of the invention, in that valve operation is not in any sense dependent upon any relation to the instantaneous gravity vector.